Showing papers by "David A. Kass published in 2015"
TL;DR: It is shown that cGMP-selective PDE9A is expressed in the mammalian heart, including humans, and is upregulated by hypertrophy and cardiac failure, and its role in stress-induced heart disease suggests potential as a therapeutic target.
Abstract: Cyclic guanosine monophosphate (cGMP) is a second messenger molecule that transduces nitric-oxide- and natriuretic-peptide-coupled signalling, stimulating phosphorylation changes by protein kinase G. Enhancing cGMP synthesis or blocking its degradation by phosphodiesterase type 5A (PDE5A) protects against cardiovascular disease. However, cGMP stimulation alone is limited by counter-adaptions including PDE upregulation. Furthermore, although PDE5A regulates nitric-oxide-generated cGMP, nitric oxide signalling is often depressed by heart disease. PDEs controlling natriuretic-peptide-coupled cGMP remain uncertain. Here we show that cGMP-selective PDE9A (refs 7, 8) is expressed in the mammalian heart, including humans, and is upregulated by hypertrophy and cardiac failure. PDE9A regulates natriuretic-peptide- rather than nitric-oxide-stimulated cGMP in heart myocytes and muscle, and its genetic or selective pharmacological inhibition protects against pathological responses to neurohormones, and sustained pressure-overload stress. PDE9A inhibition reverses pre-established heart disease independent of nitric oxide synthase (NOS) activity, whereas PDE5A inhibition requires active NOS. Transcription factor activation and phosphoproteome analyses of myocytes with each PDE selectively inhibited reveals substantial differential targeting, with phosphorylation changes from PDE5A inhibition being more sensitive to NOS activation. Thus, unlike PDE5A, PDE9A can regulate cGMP signalling independent of the nitric oxide pathway, and its role in stress-induced heart disease suggests potential as a therapeutic target.
270 citations
TL;DR: It is revealed that pluripotent-stem-cell-derived CMs mature early in culture but are arrested at the late embryonic stage with aberrant regulation of key transcription factors, which provides a foundation for understanding CM maturation.
143 citations
TL;DR: MiR-30d increase in cardiomyocytes correlates with areas of increased wall stress in HFDYS and is protective against deleterious tumor necrosis factor signaling and is associated with response to CRT in H FDYS in this translational pilot study.
Abstract: Background—Biomarkers that predict response to cardiac resynchronization therapy (CRT) in heart failure patients with dyssynchrony (HFDYS) would be clinically important. Circulating extracellular microRNAs (miRNAs) have emerged as novel biomarkers that may also play important functional roles, but their relevance as markers for CRT response has not been examined. Methods and Results—Comprehensive miRNA polymerase chain reaction arrays were used to assess baseline levels of 766 plasma miRNAs in patients undergoing clinically indicated CRT in an initial discovery set (n=12) with and without subsequent echocardiographic improvement at 6 months after CRT. Validation of candidate miRNAs in 61 additional patients confirmed that baseline plasma miR-30d was associated with CRT response (defined as an increase in left ventricular ejection fraction ≥10%). MiR-30d was enriched in coronary sinus blood and increased in late-contracting myocardium in a canine model of HFDYS, indicating cardiac origin with maximal expre...
121 citations
TL;DR: Serum ES correlated with poor functional status, decreased exercise tolerance, and invasive hemodynamics variables, and a loss-of-function, missense variant in the gene encoding ES, Col18a1, was linked to lower circulating protein and was independently associated with reduced mortality.
Abstract: Rationale: Pulmonary arterial hypertension (PAH) is a medically incurable disease resulting in death from right ventricular (RV) failure. Both pulmonary vascular and RV remodeling are linked to dynamic changes in the microvasculature. Therefore, we hypothesized that circulating angiostatic factors could be linked to outcomes and represent novel biomarkers of disease severity in PAH.Objectives: We sought to determine the relationship of a potent angiostatic factor, endostatin (ES), with disease severity and mortality in PAH. Furthermore, we assessed genetic predictors of ES expression and/or function and their association with outcomes in PAH.Methods: We measured levels of serum ES in two independent cohorts of patients with PAH. Contemporaneous clinical data included New York Heart Association functional class, 6-minute-walk distance, invasive hemodynamics, and laboratory chemistries.Measurements and Main Results: Serum ES correlated with poor functional status, decreased exercise tolerance, and invasive ...
88 citations
TL;DR: It is reported that intact BDNF/TrkB signaling is required for the heart to fully contract and relax, and that cardiac-specific TrkB knockout mice (TrkB−/−) display impaired cardiac contraction and relaxation, showing that BDNF / TrkB signaling acts constitutively to sustain in vivo myocardial performance.
Abstract: BDNF and its associated tropomyosin-related kinase receptor B (TrkB) nurture vessels and nerves serving the heart. However, the direct effect of BDNF/TrkB signaling on the myocardium is poorly understood. Here we report that cardiac-specific TrkB knockout mice (TrkB(-/-)) display impaired cardiac contraction and relaxation, showing that BDNF/TrkB signaling acts constitutively to sustain in vivo myocardial performance. BDNF enhances normal cardiomyocyte Ca(2+) cycling, contractility, and relaxation via Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Conversely, failing myocytes, which have increased truncated TrkB lacking tyrosine kinase activity and chronically activated CaMKII, are insensitive to BDNF. Thus, BDNF/TrkB signaling represents a previously unidentified pathway by which the peripheral nervous system directly and tonically influences myocardial function in parallel with β-adrenergic control. Deficits in this system are likely additional contributors to acute and chronic cardiac dysfunction.
86 citations
TL;DR: It is demonstrated that NK cells limit eosinophilic infiltration both indirectly, through altering eOSinophil-related chemokine production by cardiac fibroblasts, and directly, by inducing eos inophil apoptosis in vitro.
Abstract: Myocarditis is a leading cause of sudden cardiac failure in young adults. Natural killer (NK) cells, a subset of the innate lymphoid cell compartment, are protective in viral myocarditis. Herein, we demonstrated that these protective qualities extend to suppressing autoimmune inflammation. Experimental autoimmune myocarditis (EAM) was initiated in BALB/c mice by immunization with myocarditogenic peptide. During EAM, activated cardiac NK cells secreted interferon γ, perforin, and granzyme B, and expressed CD69, tumor necrosis factor–related apoptosis-inducing ligand treatment, and CD27 on their cell surfaces. The depletion of NK cells during EAM with anti-asialo GM1 antibody significantly increased myocarditis severity, and was accompanied by elevated fibrosis and a 10-fold increase in the percentage of cardiac-infiltrating eosinophils. The resultant influx of eosinophils to the heart was directly responsible for the increased disease severity in the absence of NK cells, because treatment with polyclonal antibody asialogangloside GM-1 did not augment myocarditis severity in eosinophil-deficient ΔdoubleGATA1 mice. We demonstrate that NK cells limit eosinophilic infiltration both indirectly, through altering eosinophil-related chemokine production by cardiac fibroblasts, and directly, by inducing eosinophil apoptosis in vitro. Altogether, we define a new pathway of eosinophilic regulation through interactions with NK cells.
67 citations
TL;DR: It is demonstrated that myocardial PKG1α oxidation prevents a beneficial response to pathological stress, may explain variable responses to PKG2α pathway stimulation in heart disease, and indicate that maintaining PKG 1α in its reduced form may optimize its intrinsic cardioprotective properties.
Abstract: The cGMP-dependent protein kinase-1α (PKG1α) transduces NO and natriuretic peptide signaling; therefore, PKG1α activation can benefit the failing heart. Disease modifiers such as oxidative stress may depress the efficacy of PKG1α pathway activation and underlie variable clinical results. PKG1α can also be directly oxidized, forming a disulfide bond between homodimer subunits at cysteine 42 to enhance oxidant-stimulated vasorelaxation; however, the impact of PKG1α oxidation on myocardial regulation is unknown. Here, we demonstrated that PKG1α is oxidized in both patients with heart disease and in rodent disease models. Moreover, this oxidation contributed to adverse heart remodeling following sustained pressure overload or Gq agonist stimulation. Compared with control hearts and myocytes, those expressing a redox-dead protein (PKG1α(C42S)) better adapted to cardiac stresses at functional, histological, and molecular levels. Redox-dependent changes in PKG1α altered intracellular translocation, with the activated, oxidized form solely located in the cytosol, whereas reduced PKG1α(C42S) translocated to and remained at the outer plasma membrane. This altered PKG1α localization enhanced suppression of transient receptor potential channel 6 (TRPC6), thereby potentiating antihypertrophic signaling. Together, these results demonstrate that myocardial PKG1α oxidation prevents a beneficial response to pathological stress, may explain variable responses to PKG1α pathway stimulation in heart disease, and indicate that maintaining PKG1α in its reduced form may optimize its intrinsic cardioprotective properties.
63 citations
TL;DR: The data indicate important structural and functional alterations to the cardiac sarcomere and the contribution of protein citrullination to this process.
Abstract: Aims Citrullination, the post-translational conversion of arginine to citrulline by the enzyme family of peptidylarginine deiminases (PADs), is associated with several diseases, and specific citrullinated proteins have been shown to alter function while others act as auto-antigens. In this study, we identified citrullinated proteins in human myocardial samples, from healthy and heart failure patients, and determined several potential functional consequences. Further we investigated PAD isoform cell-specific expression in the heart.
Methods and results A citrullination-targeted proteomic strategy using data-independent (SWATH) acquisition method was used to identify the modified cardiac proteins. Citrullinated-induced sarcomeric proteins were validated using two-dimensional gel electrophoresis and investigated using biochemical and functional assays. Myocardial PAD isoforms were confirmed by RT-PCR with PAD2 being the major isoform in myocytes. In total, 304 citrullinated sites were identified that map to 145 proteins among the three study groups: normal, ischaemia, and dilated cardiomyopathy. Citrullination of myosin (using HMM fragment) decreased its intrinsic ATPase activity and inhibited the acto-HMM-ATPase activity. Citrullinated TM resulted in stronger F-actin binding and inhibited the acto-HMM-ATPase activity. Citrullinated TnI did not alter the binding to F-actin or acto-HMM-ATPase activity. Overall, citrullination of sarcomeric proteins caused a decrease in Ca2+ sensitivity in skinned cardiomyocytes, with no change in maximal calcium-activated force or hill coefficient.
Conclusion Citrullination unique to the cardiac proteome was identified. Our data indicate important structural and functional alterations to the cardiac sarcomere and the contribution of protein citrullination to this process.
58 citations
TL;DR: It is shown that heart failure with synchronous contraction is improved by inducing dyssynchrony for 6 hours daily by right ventricular pacing using an intracardiac pacing device, in a process called pacemaker-induced transient asynchrony (PITA), and suggested that PITA could bring the benefits of CRT to the many heart failure patients with synchronOUS contraction who are not CRT candidates.
Abstract: Uncoordinated contraction from electromechanical delay worsens heart failure pathophysiology and prognosis, but restoring coordination with biventricular pacing, known as cardiac resynchronization therapy (CRT), improves both. However, not every patient qualifies for CRT. We show that heart failure with synchronous contraction is improved by inducing dyssynchrony for 6 hours daily by right ventricular pacing using an intracardiac pacing device, in a process we call pacemaker-induced transient asynchrony (PITA). In dogs with heart failure induced by 6 weeks of atrial tachypacing, PITA (starting on week 3) suppressed progressive cardiac dilation as well as chamber and myocyte dysfunction. PITA enhanced β-adrenergic responsiveness in vivo and normalized it in myocytes. Myofilament calcium response declined in dogs with synchronous heart failure, which was accompanied by sarcomere disarray and generation of myofibers with severely reduced function, and these changes were absent in PITA-treated hearts. The benefits of PITA were not replicated when the same number of right ventricular paced beats was randomly distributed throughout the day, indicating that continuity of dyssynchrony exposure is necessary to trigger the beneficial biological response upon resynchronization. These results suggest that PITA could bring the benefits of CRT to the many heart failure patients with synchronous contraction who are not CRT candidates.
38 citations
TL;DR: Differential remodeling of cholinergic signaling represents a novel mechanism for enhancing sympathovagal balance with CRT and may identify new targets for treatment of systolic HF.
Abstract: Rationale: Cardiac resynchronization therapy (CRT) is the only heart failure (HF) therapy documented to improve left ventricular (LV) function and reduce mortality. The underlying mechanisms are incompletely understood. While β-adrenergic signaling has been studied extensively, the effect of CRT on cholinergic signaling is unexplored.
Objective: We hypothesized that remodeling of cholinergic signaling plays an important role in the aberrant calcium signaling and depressed contractile and β-adrenergic responsiveness in dyssynchronous HF (DHF) that are restored by CRT.
Methods and Results: Canine tachypaced DHF and CRT models were generated to interrogate responses specific to dyssynchronous vs. resynchronized ventricular contraction during hemodynamic decompensation. Echocardiographic, electrocardiographic and invasive hemodynamic data were collected from normal controls, DHF and CRT models. LV tissue was used for biochemical analyses and functional measurements (calcium transient, sarcomere shortening) from isolated myocytes (N=42-104 myocytes/model; 6-9 hearts/model). Human LV myocardium was obtained for biochemical analyses from explanted failing (N=18) and non-failing (N=7) hearts. The M2 subtype of muscarinic acetylcholine receptors (M2-mAChR) was upregulated in human and canine HF compared to non-failing controls. CRT attenuated the increased M2-mAChR expression and Gαi-coupling, and enhanced M3-mAChR expression in association with enhanced calcium cycling, sarcomere shortening and β-adrenergic responsiveness. Despite model-dependent remodeling, cholinergic stimulation completely abolished isoproterenol-induced triggered activity in both DHF and CRT myocytes.
Conclusions: Remodeling of cholinergic signaling is a critical pathological component of human and canine HF. Differential remodeling of cholinergic signaling represents a novel mechanism for enhancing sympathovagal balance with CRT and may identify new targets for treatment of systolic HF.
37 citations
TL;DR: It is hypothesized that CRT invokes protective or advantageous pathways that can be reflected in the circulating proteome, and glycoproteins such as alpha‐fetoprotein, alpha‐2‐macroglobulin, galectin‐3‐binding protein, and collectin‐10 show association to failing heart and CRT treatment model.
Abstract: Conduction abnormalities can lead to dyssynchronous contraction, which significantly worsens morbidity and mortality of heart failure. Cardiac resynchronization therapy (CRT) can reverse ventricular remodeling and improve cardiac function. Although the underlying molecular changes are unknown, the use of a canine model of dyssynchronous heart failure (DHF) and CRT has shown that there are global changes across the cardiac proteome. This study determines changes in serum glycoprotein concentration from DHF and CRT compared to normal. We hypothesize that CRT invokes protective or advantageous pathways that can be reflected in the circulating proteome. Two prong discovery approaches were carried out on pooled normal, DHF, and CRT samples composed of individual canine serum to determine the overall protein concentration and the N-linked glycosites of circulating glycoproteins. The level of the glycoproteins was altered in DHF and CRT compared to control sera, with 63 glycopeptides substantially increased in DHF and/or CRT. Among the 32 elevated glycosite-containing peptides in DHF, 13 glycopeptides were reverted to normal level after CRT therapy. We further verify the changes of glycopeptides using label-free LC-MS from individual canine serum. Circulating glycoproteins such as alpha-fetoprotein, alpha-2-macroglobulin, galectin-3-binding protein, and collectin-10 show association to failing heart and CRT treatment model.
TL;DR: SGC and cGMP-dependent signaling are necessary and sufficient for HNO-induced vasodilation in vivo but are not required for positive inotropic action.
Abstract: Nitroxyl (HNO), the reduced and protonated form of nitric oxide (NO·), confers unique physiological effects including vasorelaxation and enhanced cardiac contractility. These features have spawned current pharmaceutical development of HNO donors as heart failure therapeutics. HNO interacts with selective redox sensitive cysteines to effect signaling but is also proposed to activate soluble guanylate cyclase (sGC) in vitro to induce vasodilation and potentially enhance contractility. Here, we tested whether sGC stimulation is required for these HNO effects in vivo and if HNO also modifies a redox-sensitive cysteine (C42) in protein kinase G-1α to control vasorelaxation. Intact mice and isolated arteries lacking the sGC-β subunit (sGCKO, results in full sGC deficiency) or expressing solely a redox-dead C42S mutant protein kinase G-1α were exposed to the pure HNO donor, CXL-1020. CXL-1020 induced dose-dependent systemic vasodilation while increasing contractility in controls; however, vasodilator effects were absent in sGCKO mice whereas contractility response remained. The CXL-1020 dose reversing 50% of preconstricted force in aortic rings was ≈400-fold greater in sGCKO than controls. Cyclic-GMP and cAMP levels were unaltered in myocardium exposed to CXL-1020, despite its inotropic-vasodilator activity. In protein kinase G-1α(C42S) mice, CXL-1020 induced identical vasorelaxation in vivo and in isolated aortic and mesenteric vessels as in littermate controls. In both groups, dilation was near fully blocked by pharmacologically inhibiting sGC. Thus, sGC and cGMP-dependent signaling are necessary and sufficient for HNO-induced vasodilation in vivo but are not required for positive inotropic action. Redox modulation of protein kinase G-1α is not a mechanism for HNO-mediated vasodilation.
TL;DR: In this paper, the authors investigated potential labeling bias in the existing methods with a single tag to detect SNO, explore if there are distinct cysteine subpopulations, and then, develop a strategy to maximize the coverage of SNO proteome.
Abstract: Rationale:S-nitrosylation (SNO), an oxidative post-translational modification of cysteine residues, responds to changes in the cardiac redox-environment. Classic biotin-switch assay and its derivatives are the most common methods used for detecting SNO. In this approach, the labile SNO group is selectively replaced with a single stable tag. To date, a variety of thiol-reactive tags have been introduced. However, these methods have not produced a consistent data set, which suggests an incomplete capture by a single tag and potentially the presence of different cysteine subpopulations. Objective:To investigate potential labeling bias in the existing methods with a single tag to detect SNO, explore if there are distinct cysteine subpopulations, and then, develop a strategy to maximize the coverage of SNO proteome. Methods and Results:We obtained SNO-modified cysteine data sets for wild-type and S-nitrosoglutathione reductase knockout mouse hearts (S-nitrosoglutathione reductase is a negative regulator of S-n...
TL;DR: IodoDPA is a promising new imaging agent for atherosclerosis, with specificity for the macrophage component of the lesions involved, and is used to detect both intravascular macrophages andmacrophage infiltrates within the myocardium in the ApoE -/- mouse model of Atherosclerosis.
TL;DR: This study provides the first identification of a myocardial-specific PKGI&agr; LZ-dependent antiremodeling substrate and supports further exploration of PKGI; myocardian LZ substrates as potential therapeutic targets for heart failure.
Abstract: Background— Pharmacological activation of cGMP-dependent protein kinase G I (PKGI) has emerged as a therapeutic strategy for humans with heart failure. However, PKG-activating drugs have been limited by hypotension arising from PKG-induced vasodilation. PKGIα antiremodeling substrates specific to the myocardium might provide targets to circumvent this limitation, but currently remain poorly understood.
Methods and Results— We performed a screen for myocardial proteins interacting with the PKGIα leucine zipper (LZ)–binding domain to identify myocardial-specific PKGI antiremodeling substrates. Our screen identified cardiac myosin–binding protein-C (cMyBP-C), a cardiac myocyte–specific protein, which has been demonstrated to inhibit cardiac remodeling in the phosphorylated state, and when mutated leads to hypertrophic cardiomyopathy in humans. GST pulldowns and precipitations with cGMP-conjugated beads confirmed the PKGIα–cMyBP-C interaction in myocardial lysates. In vitro studies demonstrated that purified PKGIα phosphorylates the cMyBP-C M-domain at Ser-273, Ser-282, and Ser-302. cGMP induced cMyBP-C phosphorylation at these residues in COS cells transfected with PKGIα, but not in cells transfected with LZ mutant PKGIα, containing mutations to disrupt LZ substrate binding. In mice subjected to left ventricular pressure overload, PKGI activation with sildenafil increased cMyBP-C phosphorylation at Ser-273 compared with untreated mice. cGMP also induced cMyBP-C phosphorylation in isolated cardiac myocytes.
Conclusions— Taken together, these data support that PKGIα and cMyBP-C interact in the heart and that cMyBP-C is an anti remodeling PKGIα kinase substrate. This study provides the first identification of a myocardial-specific PKGIα LZ-dependent antiremodeling substrate and supports further exploration of PKGIα myocardial LZ substrates as potential therapeutic targets for heart failure.
TL;DR: Patients with scleroderma–associated pulmonary arterial hypertension have worse survival than patients with idiopathic PAH and it is hypothesized that the right ventricle (RV) adapts differently in SSc-PAH versus IPAH, which may in part explain previously observed decreased contractility and poorer survival.
Abstract: Patients with scleroderma (SSc)–associated pulmonary arterial hypertension (PAH) have worse survival than patients with idiopathic PAH (IPAH). We hypothesized that the right ventricle (RV) adapts differently in SSc-PAH versus IPAH. We used cardiac magnetic resonance imaging (cMRI) and hemodynamic characteristics to assess the relationship between RV morphology and RV load in patients with SSc-PAH and IPAH. In 53 patients with PAH (35 with SSc-PAH and 18 with IPAH) diagnosed by right heart catheterization (RHC), we examined cMRIs obtained within 48 hours of RHC and compared RV morphology between groups. Regression analysis was used to assess the association between diagnosis (IPAH vs. SSc-PAH) and RV measurements after adjusting for age, sex, race, body mass index (BMI), left ventricular (LV) mass, and RV load. There were no significant differences in unadjusted comparisons of cMRI measurements between the two groups. Univariable regression showed RV mass index (RVMI) was linearly associated with m...
TL;DR: Hospitalized patients with HFpEF from an urban population develop a high rate of WRF are younger than previous cohorts, often black, and have greater co-morbidities than previously described.
Abstract: Heart failure with preserved ejection fraction (HFpEF) has been described as a disease of elderly subjects with female predominance and hypertension. Our clinical experience suggests patients with HFpEF from an urban population are far more heterogenous, with greater co-morbidities and significant inhospital morbidity. There are limited data on the hospitalization course and outcomes in acute decompensated HFpEF. Hospitalizations for acute heart failure at our institution from July 2011 to June 2012 were identified by International Classification of Diseases, Ninth Revision, codes and physician review for left ventricular ejection fraction ≥50% and were reviewed for patient characteristics and clinical outcomes. Worsening renal function (WRF) was defined as creatinine increase of ≥0.3 mg/dl by 72 hours after admission. Hospital readmission and mortality data were captured from electronic medical records and the Social Security Death Index. Of 434 heart failure admissions, 206 patients (47%) with HFpEF were identified. WRF developed in 40%, the highest reported in HFpEF to date, and was associated with higher blood pressure and lower volume of diuresis. Compared to previous reports, hospitalized patients with HFpEF were younger (mean age 63.2 ± 13.6 years), predominantly black (74%), and had more frequent and severe co-morbidities: hypertension (89%), diabetes (56%), and chronic kidney disease (55%). There were no significant differences in 1- and 12-month outcomes by gender, race, or WRF. In conclusion, we found hospitalized patients with HFpEF from an urban population develop a high rate of WRF are younger than previous cohorts, often black, and have greater co-morbidities than previously described.
TL;DR: Treatment with an AT1R blocker, losartan, selectively reversed the signaling changes and ameliorated adverse phenotypic effects in the combination of aging and inflammation as well as each independently.
Abstract: // Tyesha N. Burks 1 , Ruth Marx 1 , Laura Powell 1 , Jasma Rucker 2 , Djahida Bedja 2 , Elisa Heacock 1 , Barbara J. Smith 3 , D. Brian Foster 2 , David Kass 2 , Brian O’Rourke 2 , Jeremy D. Walston 1 , Peter M. Abadir 1 1 Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA 2 Division of Cardiology, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA 3 Cell Biology Imaging Facility, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA Correspondence to: Peter M. Abadir, e-mail: pabadir1@jhmi.edu Keywords: aging, mitochondria, AT1R, inflammation, heart Received: April 4, 2015 Accepted: May 06, 2015 Published: May 18, 2015 ABSTRACT Although the effects of aging and inflammation on the health of the cardiac muscle are well documented, the combined effects of aging and chronic inflammation on cardiac muscle are largely unknown. The renin-angiotensin system (RAS) has been linked independently to both aging and inflammation, but is understudied in the context of their collective effect. Thus, we investigated localized cardiac angiotensin II type I and type II receptors (AT 1 R, AT 2 R), downstream effectors, and phenotypic outcomes using mouse models of the combination of aging and inflammation and compared it to a model of aging and a model of inflammation. We show molecular distinction in the combined effect of aging and inflammation as compared to each independently. The combination maintained an increased AT 1 R:AT 2 R and expression of Nox2 and exhibited the lowest activity of antioxidants. Despite signaling pathway differences, the combined effect shared phenotypic similarities with aging including oxidative damage, fibrosis, and hypertrophy. These phenotypic similarities have dubbed inflammatory conditions as premature aging, but they are, in fact, molecularly distinct. Moreover, treatment with an AT 1 R blocker, losartan, selectively reversed the signaling changes and ameliorated adverse phenotypic effects in the combination of aging and inflammation as well as each independently.
TL;DR: Left ventricular (LV) dilation was blunted by sildenafil with end–systolic diameter being significantly smaller and fractional shortening improved in rats with AR when treatment is initiated early.
Abstract: Currently there is no reliable medical treatment for aortic regurgitation (AR). Thirty-nine Sprague–Dawley rats underwent
creation of AR or sham operation. Treated rats were assigned to early or late institution of sildenafil therapy (100 mg/kg/day) for a total of 10 weeks. Treatment–effects were measured by serial echocardiography, invasive hemodynamic measurements, and tissue analysis. Rats assigned to early treatment developed less remodeling than untreated rats. Thus, left ventricular (LV) dilation was blunted by sildenafil with end–systolic diameter being significantly smaller (6.6 ± 0.4 vs. 7.7 ± 0.4 mm, respectively, p < 0.05). Also, LV wall thickness was significantly decreased in treated rats compared to controls (2.23 ± 0.08 vs. 2.16 ± 0.05 mm, p < 0.01). Fractional shortening was improved by treatment (p < 0.05). Myocardial fibrosis was borderline decreased by treatment (p = 0.09). Akt was increased in treated compared to controls (p < 0.05). Sildenafil slightly inhibits LV remodeling and improves fractional shortening in rats with AR when treatment is initiated early.
TL;DR: There was no statistically significant difference in directly measured myocardial oxygen consumption preceding and following omecamtiv mecarbil administration, and in contrast to the prior work in a conscious dog model of heart failure, the authors studied animals with systolic heart failure.
Abstract: We reviewed the article, “Myosin Activator Omecamtiv Mecarbil Increases Myocardial Oxygen Consumption and Impairs Cardiac Efficiency Mediated by Resting Myosin ATPase Activity,”1 with interest because its conclusions differ from those in our work published in this same journal2 and elsewhere.3 We commend the authors for pursuing an important question related to an investigational drug being studied in patients with systolic heart failure. However, we think deficiencies in their experimental approach undermine their conclusions.
First, despite the title of the article, there was no statistically significant difference in directly measured myocardial oxygen consumption preceding and following omecamtiv mecarbil administration (Table 2 in Bakkehaug et al1). In contrast to the prior work in a conscious dog model of heart failure,2 the authors studied animals …
TL;DR: Current understanding of dyssynchrony and CRT cellular and subcellular mechanisms are reviewed, arguing that these aspects are key to improving CRT use, as well as translating its benefits to a wider HF population.
TL;DR: Growing evidence has positioned the myocyte as a “Master and Commander” for coordinating interstitial responses to myocardial stress, including fibrosis, vascular remodeling, and inflammation.
Abstract: Heart failure is a global health problem, with an estimated 30–50 million patients diagnosed worldwide (1, 2). Therapeutic advances have reduced early mortality; however, morbidity caused by damaged or failing ventricles remains high. Indeed, heart failure is the most common cause for hospitalization in elderly individuals, with recalcitrant 5-y survival rates remaining worse than most cancers (2). Sustained stress from abnormal mechanical load, neurohormone stimulation, and genetic defects are all potent inducers of heart failure (3, 4). These trigger conversations among vascular, muscle, and inflammatory cells, as well as fibroblasts using a myokine/cytokine vocabulary that can be shared by the multiple cell types or be more specific. As recently reviewed by Ghigo et al. (5), growing evidence has positioned the myocyte as a “Master and Commander” for coordinating interstitial responses to myocardial stress, including fibrosis, vascular remodeling, and inflammation. In hearts subjected to pressure overload, myocyte secretion of interleukins (IL-1β, -6, -18), TNF-α, receptor activator of NF-κB ligand, and macrophage chemoattractant protein-1 all signal to inflammatory responses, whereas ischemic disease engages additional factors, such as the adhesion molecules ICAM-1 and VCAM-1, and anti-inflammatory growth differentiation factor 15 (5). Depending on the stress, this coordinated inflammatory conversation can impact myocyte growth and survival, as well as remove damaged or dead cells.
TL;DR: Identifying novel PKGIα LZ substrates, like MLK3, may reveal new candidate therapeutic targets for hypertension and heart failure, and reveal that deletion ofMLK3 leads to hypertension and pathologic cardiac hypertrophy.
Abstract: Protein kinase G I alpha (PKGIα) counteracts hypertension and pathologic cardiac remodeling. These effects require the PKGIα leucine zipper (LZ) protein binding domain. However, PKGIα LZ-binding substrates mediating these effects remain incompletely understood. We previously demonstrated that Mixed Lineage Kinase 3 (MLK3) binds the PKGIα LZ domain in the heart. In the present study we hypothesized that MLK3 functions as a PKGIα substrate and cardiovascular effector.
We observed that recombinant MLK3 precipitated with affinity purified PKGIα but not with LZ mutant PKGIα. When PKGIα was precipitated with RP-cGMP beads, which inhibit PKG kinase activity, we observed decreased PKGIα-MLK3 co-precipitation, supporting a requirement of PKGIα kinase activity for MLK3-PKGIa interaction. PKGIα phosphorylated MLK3 in vitro as assayed by Western blot.
We next analysed mice with genetic deletion of MLK3. In the baseline state, MLK3-/- mice display normal cardiac function as assessed by echocardiography and invasive cardiac hemodynamics. MLK3-/- mice develop cardiac hypertrophy by 3 months of age (heart weight/tibia length 64.4 ± 1.9 mg/cm WT, 73.6 ± 2.1 mg/cm MLK3-/-; p<0.001; n=11 WT, 14 MLK3-/-). Compared with WT littermates, anesthetized MLK3-/- mice have elevated blood pressure (BP) (94.3 ± 2.1 mmHg WT, 109.3 ± 2.5 mmHg MLK3-/-; p<0.001). Conscious male MLK3-/- mice monitored continuously with implantable arterial radiotelemetry (10-12 weeks of age) had overt hypertension compared with WT littermates (Systolic BP: WT 121.5 ± 2.0 mmHg, MLK3-/- 161.6 ± 5.1 mmHg; p<0.01; Diastolic BP: WT 87.0 ± 2.9 mmHg, MLK3-/- 114.5 ± 2.7 mmHg; p<0.001; n=4 WT, 3 MLK3-/-). We observed no difference in baseline heart rate between genotypes.
Chronic administration of hydralazine (250 mg/L) normalized BP in MLK3-/- mice, but did not completely inhibit cardiac hypertrophy. Further, in response to LV pressure overload by transaortic constriction (TAC), which equalized left ventricular (LV) systolic pressure between genotypes, MLK3-/- mice had increased LV hypertrophy (LV/Tibia length) as well as elevated LV end diastolic pressure, and worsening of LV ejection fraction, preload recruitable stroke work, and other LV systolic and diastolic indices (n=8-10), indicating advanced cardiac dysfunction.
Together, our findings identify MLK3 as a direct PKGI substrate, and reveal that deletion of MLK3 leads to hypertension and pathologic cardiac hypertrophy. These findings support a model in which, in response to activation by PKGIα, MLK3 inhibits hypertension and cardiac hypertrophy. We conclude that identifying novel PKGIα LZ substrates, like MLK3, may reveal new candidate therapeutic targets for hypertension and heart failure.
01 Jan 2015
TL;DR: The journal published publishes results of a wide variety of studies from human and from informative model Physiological Genomics, with techniques linking genes and pathways to physiology.
Abstract: 24 times a year (twice monthly) by the American Physiological Society, 9650 Rockville Pike, Bethesda MD systems with techniques linking genes and pathways to physiology, from prokaryotes to eukaryotes. It is published publishes results of a wide variety of studies from human and from informative model Physiological Genomics
TL;DR: The name, slow force response (SFR), has indeed been adapted by many to describe this behavior, but it is felt the term is far less universal than the writers suggest, and also believe it obfuscates the mechanistic concepts behind it.
Abstract: As Drs. Villa-Abrille, Perez, and Cingolani correctly point out,1 the behavior whereby cardiac muscle is subjected to abruptly increased systolic load and then manifests a gradual rise in contractility has been recognized for over a century. First credited to Gleb (not Glen) von Anrep,2 its name has morphed over the decades along with the types of experiments used to generate it. The name, slow force response (SFR), has indeed been adapted by many to describe this behavior, but we feel the term is far less universal than the writers suggest, and also believe it obfuscates the mechanistic concepts behind it. What is slow—force or response? What is the response to and what …